Liposomes In Drug Delivery

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Liposomes In Drug Delivery

• Mahmoud R. Jaafari, PhD
• Prof. of Pharmaceutics
• School of Pharmacy
• Mashhad University of Medical Sciences

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Overview

• Definition of liposomes
• Classification of liposomes
• Structure of liposomes
• Preparation of liposomes
• Purification of liposomes
• Characterization of liposomes
• Liposome-cell interaction
• Liposomes as drug delivery systems
• Targeted Drug Delivery

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Definition

• Liposomes are spherical microscopic vesicles
  consisting phospholipids bilayers which enclose
  aqueous compartments

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Classification

• Small unilamellar vesicles (SUV), 25 to 100 nm in
  size that consist of a single bilayer
• Large unilamellar vesicle (LUV), 100 to 500 nm in
  size that consist of a single bilayer
• Multilamellar vesicle (MLV), 200 nm to several
  microns,that consist of two or more concentric
  bilayer

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• Described by Bangham in 1965
• Study of membranes

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Structure of Liposomes Phospholipids
Polar Head Groups
Three carbon glycerol
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Structure of Liposomes Phospholipids
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Phase Transition Temperature Tm
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Phase Transition Temperature Tm
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Membrane permeability
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Cholesterol

• Because of its rigid steroid ring system which
  interferes with motion of fatty acid tails,
  stabilizes the lipid bilayer and decrease the
  leakage of encapsulated drug

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DSC of Chol/DSPC
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Non Structural Components
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Preparation of liposomes Mechanical Dispersion
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Processing of lipids hydrated (MLVs) by physical
means

• Micro-emulsification of liposomes

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Processing of lipids hydrated (MLVs) by physical
means

• EmulsiFlex High Pressure Homogenizar

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Processing of lipids hydrated (MLVs) by physical
means EmulsiFlex High Pressure Homogenizar
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Purification of Liposomes
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Purification of Liposomes

• Gel Filtration Column Chromatography

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Purification of Liposomes

• Dialysis

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Purification of Liposomes

• Centrifugation

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Stability of Liposomes

• Chemical degradation
• Physical degradation
• Prevention of chemical degradation
• Prevention of physical degradation

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Preparation of Sterile Liposomes
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Liposome Characterization

• Determination of Drug Content
• Determination of Percent Capture
• Lamellarity
• Phosphate assay
• Cholesterol assay

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Liposome characterization

• Size distribution
• Zeta potential
• Tm by DSC
• Stability Drug, lipid and liposome

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Liposome-cell interaction
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Liposomes in drug delivery

• Protect the encapsulated drug from metabolic
  degradation
• Increase the half-life of drug
• Reduce the systemic toxicity of drugs
• Could be used as sustained release vehicles
• It is possible to target them to selected tissues
  or cell
• Biodegradable and biocompatible

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Types of liposomes
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Stealth or PEG-Liposomes